Numbers in parentheses represent references presented at the end of this specification. These references are incorporated as if fully set forth herein. The citation of any reference herein should not be construed as an admission that such reference is available as “Prior Art” to the instant application.
Tropomyosins are microfilament-associated proteins present in all eukaryotic cells with organ specific isoforms and distinct functions (1-3). A human fibroblast cell line expresses at least eight tropomyosin isoforms termed hTM1, hTM2, hTM3, hTM5a, hTM5a, hTM5b, hTM4, and hTM5, which are encoded by 4 different genes (3,4). The tropomyosin molecule is almost a fully α-helical protein with multiple heptad repeats and capable of forming a coiled coil dimer (5). These features appear to be associated with many known autoantibody epitopes and may contribute to autoantigenic potential (6). Indeed, several observations suggest that tropomyosin is an autoantigen for ulcerative colitis (7-10). Autoantibodies against tropomyosins are found in sera of individuals with ulcerative colitis (UC) and in IgG produced by the cultured lamina propria mononuclear cells that infiltrate the inflamed UC tissue. Furthermore, autoantibody to tropomyosin is also found in a mouse model for human UC, created by targeting deletion of the T-cell receptor α (TCRα) gene (11). Thus, the next questions are: which tropomyosin isoform or more specifically, which epitope can be recognized by these autoantibodies; and whether there is a specific tropomyosin isoform existing in UC tissue. Recently, using a limited number of tropomyosin isoform-specific monoclonal antibodies, it was demonstrated that colonic epithelial cells synthesize major tropomyosin isoforms of hTM4 and hTM5, whereas colonic smooth muscles contain at least hTM1, hTM2, and hTM3 isoforms (9). Using recombinant tropomyosin isoforms, it was further shown that UC patients produce significant autoantibodies preferentially against hTM5 (9,12).
Therefore, a need exists to identify sensitive and specific biomarkers for the diagnosis, to assess severity and predict the outcome of alimentary canal-related conditions in living subjects. Additionally, there is a clear need for new drug discovery assays, and for therapeutic agents for alimentary canal-related conditions that work quickly, potently, specifically, and with fewer side effects. Accordingly, it is toward the fulfillment of the foregoing and other objectives that the present invention is directed.